Battery packs, also referred to as battery modules, have been used for years in a variety of industries and technologies that include everything from portable electric tools and laptop computers to small hand-held electronic devices such as cell phones, MP3 players, and GPS units. In general, a battery pack is comprised of multiple individual batteries, also referred to as cells, contained within a single piece or multi-piece housing. Single piece housings are often comprised of shrink-wrap while multi-piece housings often rely on a pair of complementary housing members that are designed to fit tightly around the cells when the housing members are snapped or otherwise held together. Typically a conventional battery pack will also include means to interconnect the individual cells as well as circuitry to enable charging and/or to protect against overcharging.
Battery packs offer a number of advantages over the use of individual battery cells. From the end user's perspective, combining multiple cells into a single housing simplifies battery removal, replacement and/or battery recharging, since the user is only required to deal with a single unit. From the manufacturer's perspective, the use of battery packs provides additional marketing flexibility. For example, a manufacturer may offer a variety of interchangeable battery packs at different price points for the same device(s), the different battery packs providing different capacities, cell types (e.g., lithium ion versus nickel-metal-hybrid), or other variations. A manufacturer may also find it advantageous to market multiple devices that all utilize a single, interchangeable battery pack.
Recent advances in the development of hybrid and electric vehicles have lead to the need for a new type of battery pack, one capable of housing tens to hundreds of individual cells and surviving the inherent thermal and mechanical stresses of a car for a period of years. Additionally, while the housing used to package a multi-cell vehicle battery must be structurally sound enough to allow battery pack inspection and/or replacement, it must do so with minimal weight since hybrids and electric cars are exceptionally sensitive to excess weight. Lastly, the design of a vehicle battery pack should lend itself to efficient, and preferably automated, manufacturing practices. The present invention provides such a battery pack.